Coronary artery stenosis is primarily due to deposits of cholesterol, calcium and fibrotic tissue. The fibrotic tissue is usually the dominate of the three components and is a tightly composed matrix that, when incised, maintains its integrity on each side of the incision. Dilation of stenoses using standard angioplasty balloons has enjoyed widespread acceptance in the treatment of stenoses, however, this treatment protocol suffers from a high rate of restenosis. Recent studies, however, indicate that restenosis can be prevented by first incising the material that is creating the stenosis followed by dilation of the incised stenosis. After incision, a stenosis is more easily flattened, and the likelihood of damaging the artery during dilation is reduced. In most applications, incision lengths of up to approximately fifteen millimeters (15 mm) are required, followed by dilation of the incised stenosis.
Heretofore, developments have been made to equip angioplasty balloons with cutting edges, or atherotomes, which are intended to incise a stenosis subsequent to a dilation procedure. For example, U.S. Pat. No. 5,196,024 to Barath entitled “BALLOON CATHETER WITH CUTTING EDGE,” which is assigned to the assignee of the present invention, discloses an inflatable angioplasty balloon having a number of atherotomes mounted longitudinally on the surface of the balloon. During inflation of the Barath balloon, the atherotomes move radially to induce a series of longitudinal cuts into the surface of the stenotic material. However, when incisions of up to fifteen millimeters (15 mm) are prescribed, the Barath design requires long atherotomes due to the fact that the Barath blades only cut during radial blade movements. Unfortunately, these long, rigid blades (i.e. 10-15 mm) reduce the flexibility of the apparatus making it more difficult to guide the dilation balloon and blades through the vascular conduits to the site of the stenosis. In general, blades longer than about 4 mm have a tendency to reduce the flexibility of an apparatus such that a considerable number of operations fail due to the inability of the surgeon to navigate the tortuous vascular conduits and position the blades and balloon at the site of the stenosis.
In light of the above, it is an object of the present invention to provide an apparatus for incising a stenosis in a vascular conduit of a patient. It is a further object of the present invention to provide an apparatus for incising a stenosis having relatively short incising blades that, due to their small size can be easily guided through tortuous vascular conduits to the site of the stenosis. It is still another object of the present invention to provide an apparatus for incising a stenosis that can be adjusted, in situ to vary the incision depth. It is yet another object of the present invention to provide an apparatus for incising a stenosis that car also dilate the incised stenosis. It is another object of the present invention to provide an apparatus for incising a stenosis which is relatively simple to manufacture, is easy to use, and is comparatively cost effective.